If you have suphp, then you can check which users script will make more resources , otherwise you need to write script to find all from /proc . Also make sure services like mysql , exim , backup ,etc,. are not making the server load .

In WHM, go to System Health and click on Process Manager ("Show Current CPU Usage" in versions 11.25.0 and earlier). This will show you the processes consuming the most CPU resources, which often directly correlates with causing server load.

If you have a recent installation of cPanel/WHM then SuPHP and SuExec are enabled. Otherwise, you can enable SuPHP and SuExec by enabling SuPHP on Step 5 of EasyApache.